Abrasive articles with iron sulfide and potassium aluminum fluoride filler



United States Patent 3,246,970 ABRAEilVE ARTICLES WITH IRON SULFIDE AND POTASSIUM ALUMINUM FLUORIDE FILLER Roy Edward Zimmerman, Tonawanda, N.Y., assiguor to The Carborundum Company, Niagara Falls, N.Y., a corporation of Delaware No Drawing. Filed July 24, 1963, Ser. No. 297,210 9 Claims. (Cl. 51--298) This application is a continuation-in-part of application Serial No. 131,726, filed August 16, 1961, and now abandoned.

This invention relates to abrasive articles such as grinding wheels. More particularly, it relates to grinding wheels in which abrasive grains are bonded together and a novel and improved filler is interspersed throughout the bonded mass.

The use of fillers to improve the properties of bonded abrasive wheels is Well known in the art. These fillers serve two distinct purposes. First, fillers improve the quality of the abrasive wheel by enabling an abrasive wheel to remove metal from a work piece at an increased rate or with a reduced wheel wear per unit of metal removed or both. Thus, the fillers improve the eificiency of the abrasive wheel and therefore the economy of the grinding operation. Second, fillers improve the quality of abrasive cuts. A large amount of heat is generated when an abrasive wheel is used to cut metal.

'If this heat is not readily and quickly removed from the surface of the .cut, the metal being cut will be burned, causing discoloration of the metal near the cut and possibly a modification in the properties of the metal. Fillers assist in transferring the heat generated by the cutting operation away from the cutting surface and thereby help to minimize this danger.

Many fillers have been suggested for use in bonded abrasive articles. The most widely used filler is .cryolite, a double fluoride of sodium'and aluminum. The art also suggests the use of iron sulfides and alkali metal fluoborates. Various combinations have also been-suggested 3,246,970 Patented Apr. 19, 1966 minum fluoride in bonded abrasive articles gives superior esults to those achieved by the use of either compound alone.

The filler of this invention has been used with markedly superior results in grinding wheels for cutting-oif operations, the wheels comprising abrasive grain bonded with a thermosetting resin bond. However, other grinding wheels such as snagging wheels, raceway wheels and the like and other abrasive bodies may be made in accordance with this invention, using any of the conventional abrasives, for example silicon carbide or other hard carbides, alumina in any of its forms including furnace fused alumina, corundum and emery. Organic bonds selected from the group consisting of thermosetting resins, rubber and shellac, which are conventionally used in the manufacture of bonded abrasive bodies, may be used in this invention. elude, for example, bonds that are based on phenolic resins and amine formaldehyde resins.

The mixture of iron sulfide and potassium aluminum fluoride may be incorporated in the bond of bonded abrasive articles in amounts from about 5% to about 60% by volume of the bond and preferably in amounts ranging from 10% to by volume. Ordinarily, the higher the content of the filler, the better is the quality of the abrasive article, within the above limits. However, the quantity of filler may also be limited by the paras fillers for abrasive wheels. For example, iron sulfide and .cryolite have been suggested. Combinations of potassium fluoborate and iron sulfide and the alkali metal salts of sulfuric, hydrochloric and hydrobromic acids with lead sulfide or antimony sulfide have also been suggested.

An object of the present invention is to provide an abrasive article characterized by improved cutting rate and etficiency.

' Another object of the invention is to provide an abrasive grinding Wheel containing a novel filler that confers improved grinding properties to the wheel.

A further object of the invention is to provide a filler for grinding wheels and other abrasive products which improves the cutting rate and eificiency thereof.

Other objects and advantages of the present invention will be apparent from the following disclosure.

In accordance with the present invention it has been discovered that the cutting rate and efiiciency of abrasive articles, such as grinding wheels, may be materially improved by incorporating therein a filler comprising an intimate mixture of iron sulfide and potassium aluminum fluoride interspersed throughout the bond. More particularly, surprisingly improved results have been achieved with an intimate mixture of by volume potassium aluminum fluoride and 50% by volume pyrites used as a filler for bonded abrasive wheels of the cut-ofi type.

It has ,been found that use of these materials in admixture as fillers in grinding wheels is not only superior to "cryolite and pyrites which have been used as fillers in the past, but also it exhibits a distinct synergistic effect. Thus, the combination of iron sulfide and potassium aluticular requirements of a given abrading operation. Resinoid bonded cut-off wheels have been successfully made and tested utilizing 34% resin, 15.5% filler and 50.5% abrasive grain on a volume basis.

The amount of iron sulfide and potassium aluminum fluoride in the filler mixture may vary considerably. Resin bonded wheels have been successfully made and tested utilizing from about 25% to by volume iron sulfide particles and from about 25 to about 75 by volume potassium aluminum fluoride particles in the filler mixture. However, it is preferred to use a filler comprising 50% by volume iron sulfide and 50% by volume potassium aluminum fluoride, for at these percentages the synergistic effect of the filler mixture is most outstandmg. .The iron sulfide in the filler mixture should be finer than 200 mesh, and it is preferred that it be 325 mesh and finer. In general, the potassium aluminum fluoride should be finer than about mesh. The abrasive grain used in forming the abrasive articles may vary in size and amount in accordance with the use to which the bonded abrasive body is to be put. In general, abrasive grain having a grit size of from about No. 8 grit to about No. 220 grit may be used.

While the specification will be primarily concerned with the use of pyrites as the source of iron sulfide in the tiller, other iron sulfides may, of course, be used. For example, ferrous sulfide, ferric sulfide and iron disulphide may likewise be utilized, as Well as the known minerals containing iron sulfide, such as troilite and marcasite. Pyrites is generally preferred because it is readily available and is inexpensive. It should also be noted that the potassium aluminum fluoride utilized in wheels made according to this invention is also relatively inexpensive. Thus, not only does this invention provide a filler giving improved properties, but also utilizes inexpensive materials.

Bonded abrasive articles embodying this invention may be made by the various standard procedures for making bonded abrasive wheels. Where the bond is a phenol formaldehyde resin, the bond and filler materials, with or without modifiers, may be thoroughly admixed with the abrasive grain and after thorough admixture, the mix may be placed in a mold and pressed to form an abrasive article of the desired shape. The shaped article may then Thermosetting resin bonds ina be heated to cure or mature the bond. The body thus formed comprises abrasive grain having a bond uniting the grain as an integral body with the finely divided filler interspered throughout the bond.

In order to point out more fully the nature of the present invention, the following examples are given of illustrative embodiments of grinding wheels incorporating the present invention.

EXAMPLE I Cut-off wheels embodying the present invention have been made as set forth below.

Wheel mix: Percent by weight A1 abrasive grain (30 grit) 65.00 Powdered B stage phenolic resin 10.75 Liquid phenolic resin 4.25 Iron sulfide (325 mesh and finer) 12.70

Thus, four identical sets of wheels were made, that is identical except that a difierent filler was used for each set of wheels.

The abrasive grain, grit alumina, in each case was first wet with a solvent of furfural and cresol and the abrasive grain then thoroughly mixed with a liquid phenolic resin in order to coat the grains. A powdered B stage phenolic resin and the finely divided filler were separately blended in a mixer and the wetted abrasive was then mixed with the blended powders to coat the abrasive grains with the blended granular materials. The resulting mixture was then molded at a pressure of about 3000 p.s.i. to form wheels, according to standard procedures used in the manufacture of resinoid bonded abrasive wheels. The molded wheels were then cured at a temperature of about 350 to 400 F. for a period of about 36 hours.

The wheels thus made were 16 inches in diameter and Ms inch thick and had a 1 inch diameter arbor hole. An equal number of wheels of each type was employed in a Campbell cut-off machine, using as a work piece a 1 inch diameter rod of C1020 cold finished steel. Wheels of each group were tested under the same uniform operating conditions at a wheel speed of 3300 rpm. Eighty cuts were made on a work piece with each wheel at a rate of one second per cut, with no cutting fluid used for any of the wheels. The results observed are tabulated below.

Table I Filler Type Potassium F952 Cryollte Aluminum FeS Potassium Fluoride Cryolite Aluminum Fluoride Filler percent by volume of bond. 31. 9 31. 9 31.9 9 Volume percent ratio of total filler used 100 100 :50 50:5 No.ofeuts/sq.1nabras1veused 14.1 13.7 15.0 20. 2 V011. metal removed/ vol. abrasive 0s 4. 32 4.1 4. 59 6- 18 Relative cificiency of filler systems, 9

percent 94.0 91.0 p 100 134- 5 abrasive with the blended powdered materials. The re- The data of Table I clearly shows that the iron sulfide sulting mixture is then loaded into a suitable mold and cold pressed at about 3000 psi. to form a wheel 16 inches in diameter x inch thick with a 1 inch diameter central hole. The wheel thus formed is removed from the mold and cured at a temperature of about 350 to 400 F. for a period of about 36 hours. Wheels made in this manner have a density of about 45.5 grams per cubic inch.

EXAMPLE II To demonstrate the improved cutting ability of grinding wheels containing the novel filler of this invention over Wheels containing fillers heretofore used, four groups of bonded abrasive wheels were made, each group having a diiferent filler. One group of wheels was made using a filler of finely divided cryolite; a second group having a filler of finely divided potassium aluminum fluoride, a third group having as a filler a particulate mixture equal parts by volume of cryolite and pyrites and a fourth group having as a filler a particulate mixture of equal parts by volume of pyrites and potassium aluminum fluoride, in accordance with the present invention.

In order to provide comparative results a standard procedure was followed for making all of the bonded abrasive wheels. That is, the type, quantity and grit size of abrasive grain, type and quantity of bonding material, type and quantity of solvent, proportion of filler relative to the bonding material and standard wheel making techniques were kept constant for all the abrasive wheels.

potassium aluminum fluoride filler of this invention provides an improved cutting rate and greater efficiency over other fillers.

EXAMPLE III Another series of grinding wheels was made in accordance with the procedure described in Example II. In this series of wheels, one group of wheels was made having a particulate cryolite filler and two groups of wheels were made in which the novel filler of this invention was used. For each group of wheels the type, quantity and grit size of abrasive, type and quantity of bonding material, type and quantity of solvent, proportion of filler relative to the bonding material and standard wheel making technique were kept constant. In each case 30 grit alumina was the abrasive, phenolic resin was the bonding material and the solvent was a mixture of furfural and cresol. Thus, according to the procedure set out in Example 11, three identical sets of wheels, each 16 inches in diameter and /8 inch thick and having a one inch diameter arbor hole were made, that is, identical except that one group had a filler of finely divided cryolite while the other two groups had as a filler a finely divided mixture of equal parts by volume pyrites and potassium aluminum fluoride. The wheels thus made were subjected to standard testing conditions in which a 2 inch square hot rolled steel bar was used as the test piece. Ten cuts were made with wheels of each group and the cubic inches of metal cut per cubic inch of Wheel removed was calculated. The results are shown in Table II.

The improved cutting ability of grinding wheels containing as a filler a mixture of finely divided pyrites and potassium aluminum fluoride over wheels utilizing only the pyrites filler of the prior art is shown from the following data. The wheels were made and tested according to the procedure set forth in Example III. The wheels were similar except that one had a filler of 100% pyrites and the other had as a filler a finely divided mixture of 50% by volume pyrites and 50% by volume potassium aluminum fluoride. The results of this test are shown in Table III.

Table III Filler: Cu. in. metal/cu. in. wheel 100% pyrites 1.8

50% pyrites-50% potassium aluminum fluoride 2.2

From the foregoing description it is apparent that the novel filler of this invention improves the cutting rate and efliciency of grinding wheels. Also, when grinding wheels 'having the iron sulfide-potassium aluminum fluoride filler of this invention were used to cut metal objects, the objects showed a reduction in the amount of burn and burr as compared to the burn and burr noted when wheels having other fillers were used.

While the specification has been primarily concerned with the use of the novel filler of this invention in resin bonded wheels, it is to be understood that this novel filler can be used in all types of abrasive wheels in which a filler is commonly utilized. Thus, the filler of the present invention may be incorporated in rubber bonded grinding wheels made by any conventional process. The novel filler of this invention may also be utilized in grinding wheels having a shellac bond made by any conventional process, such as, for example a process in which abrasive grain, the filler and dry powdered shellac are mixed, placed in a mold and heated to set the shellac and bond the grain. It is also to be understood that thermosetting resins other than phenolic resins, such as, for example amine formaldehyde resins can also be used as the bond in abrasive Wheels made in accordance with this invention.

In the manufacture of cut-off wheels and other bonded abrasive bodies in accordance with this invention, it will be understood that standard manufacturing procedures for making bonded abrasive bodies are followed. Accordingly, abrasive grain, grain size, the specific bond and the proportion of grain relative to the bond may be varied in accordance with the particular application for which the bonded abrasives are intended.

The above disclosure is to be interpreted as illustrating the general principals of this invention and the preferred types and compositions of abrasive articles, and not as limitations on the invention as defined in the appended claims.

I claim:

1. An abrasive article consisting essentially of abrasive grains, an organic bond uniting the grains and a filler of iron sulfide finer than 200 mesh and potassium alumi num fluoride finer than about 100 metal interspersed throughout the bonded mass, said filler constituting from about 5% to about 60% by volume of the bond.

2. An abrasive article consisting essentially of abrasive grains, a bond selected from the group consisting of thermosetting resins, rubber and shellac uniting the grains and a filler of iron sulfide finer than 200 mesh and potassium aluminum fluoride finer than about 100 mesh interspersed throughout the bonded mass, said filler constituting from about 5% to about 60% by volume of the bond.

3. An abrasive article consisting essentially of abrasive grains, a thermosetting resin bond uniting the grains and a filler of finely divided iron sulfied or less than 200 mesh grain size and potassium aluminum fluoride of less than about 100 mesh grain size interspersed throughout the bonded mass, said filler constituting from 5% to 60% by volume of the bond.

4. An abrasive article consisting essentially of abrasive grains and a thermosetting resin bond uniting the grains, said bond having intimately associated therewith a filler consisting essentially of a mixture of finely divided pyrites of less than 200 mesh grain size and potassium aluminum fluoride of less than about 100 mesh grain size, said filler constituting from 10% to 35% by volume of the bond.

5. An abrasive article consisting essentially of abrasive grains, a bond selected from the group consisting of thermosetting resins, rubber and shellac uniting the grains and a filler interspersed throughout the bonded mass, said filler consisting essentially of a mixture of about 25% to by volume iron sulfide having a grain size of less than 200 mesh and about 75 to 25% by volume potassium aluminum fluoride having a grain size of less than about mesh, said filler constituting from about 5% to 60% by volume of the bond.

6. The article as defined in claim 5 in which the bond is a phenolic resin.

7. An abrasive article consisting essentially of abrasive grains, a thermosetting resin bond uniting the grains and a filler incorporated in the bond, said filler consisting essentially of 50% by volume of pyrites and 50% by volume of potassium aluminum fluoride, the pyrites having a grain size of less than 200 mesh and the potassium aluminum fluoride having a grain size of less than 100 mesh, said filler constituting from 10% to 35% by volume of said bond.

8. An abrasive article consisting essentially of abrasive grains, a thermosetting resin bond uniting the grains and a filler interspersed throughout the bonded mass, said filler consisting essentially of 50% by volume iron sulfide having a grain size of less than 325 mesh and 50% by volume potassium aluminum fluoride having a grain size of less than 100 mesh, said filler constituting from about 5% to 60% by volume of the bond.

9. An abrasive article consisting essentially of abrasive grains, a phenolic resin bond uniting the grains and a filler interspersed throughout the bonded mass, said filler consisting essentially of 50% by volume pyrites and 50% by volume potassium aluminum fluoride, the pyrites having a grain size less than 325 mesh and the potassium aluminum fluoride having a grain size less than 100 mesh, said filler constituting from about 10% to 35% by volume of the bond.

References Cited by the Examiner UNITED STATES PATENTS 2,308,981 1/1943 Kistler 51-307 3,032,404 5/1962 Douglass et al. 5l307 ALEXANDER H. BRODMERKEL, Primary Examiner. 

1. AN ABRASIVE ARTICLE CONSISTING ESSENTIALLY OF ABRASIVE GRAINS, AN ORGANIC BOND UNITING THE GRAINS AND A FILLER OF IRON SULFIDE FINER THAN 200 MESH AND POTASSIUM ALUMINUM FLUORIDE FINER THAN ABOUT 100 METAL INTERSPERSED THROUGHOUT THE BONDED MASS, SAID FILLER CONSTITUTING FROM ABOUT 5% TO ABOUT 60% BY VOLUME OF THE BOND. 